* remove unused function to interpolate URLs
* share function to add headers between ds/plugin proxies
* stop performing unnecessary plugin setting lookup
* fix bug causing runtime errors when using complex templated URLs
* lower case util functions not used outside of pluginproxy package
* change test URL to a (valid) dummy URL to make intent clearer
Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>
This ensures that the X-Grafana-User header can be trusted.
If the configuration enabled the setting of this header, the
server can now trust that X-Grafana-User is set/unset by Grafana.
Before this, an anonymous user could simply set the X-Grafana-User
header themselves (using the developer tool for example)
This adds support for using templated/dynamic urls in routes.
* refactor interpolateString into utils and add interpolation support for app plugin routes.
* cleanup and add error check for url parse failure
* add docs for interpolated route urls
Closes#16835
